Research Goals for the Coming Year: Within the coming year (July 1, 1980-June 30, 1981), high rates of malignant mesothelioma production may occur among the mice treated in the current year with amosite or chrysotile, because the latent period of the mesothelioma production may terminate at an early period of the coming year. If this assumption is correct, answers to major questions proposed in the overall objectives, such as the favorite sites, for the primary focus in the induced mesothelioma, structural and histochemical characterization of the mesothelioma cells at early stages of development, and the evolution of the mesothelium from normal to neoplastic, may be obtained by comprehensive observations (gross anatomy, histology, histochemistry and electron microscopy) of the periotoneum of the mice.